144 SENSE OF TOUCH. 



tain animals are supplied with whiskers for the purpose of enabling 

 them to steer clear of opposing bodies in the dark. 



SENSE OE TASTE OR GUSTATION. 



The sense of taste teaches us the quality of bodies called sapidity. 

 It is more nearly allied to touch in its mechanism than any other of the 

 senses, as it requires the immediate contact of the body with the organ 

 of taste, and the organ is, at the same time, capable of receiving tactile 

 impressions distinct from those of taste. Of this we have a striking 

 example, if we touch various portions of the tongue with the point of a 

 needle. We find two distinct perceptions occasioned. In some parts 

 the sensation of a pointed body without savour ; and in others, a me- 

 tallic taste is experienced. Pathological cases, too, exhibit, that the 

 sense of taste may be lost, whilst general sensibility remains, and con- 

 versely. The organ of gustation is not, therefore, restricted to that 

 sense, but participates in touch. Yet so distinct are those functions, 

 that touch can, in no wise, supply the place of its fellow sense, in de- 

 tecting the sapidity of bodies. This last is the immediate instruction 

 afforded by gustation. 



1. ANATOMY OF THE ORGANS OF TASTE. 



The chief organ of taste is the tongue, or rather the mucous mem- 

 brane covering the upper surface, and sides of that organ. The lips, 

 inner surface of the cheeks, palate, and fauces, participate in the func- 

 tion, especially when particular savours are concerned. M. Magendie 1 

 includes the esophagus and stomach; but we know not on what grounds: 

 his subsequent remarks, indeed, controvert the idea. The lingual 

 branch of the fifth pair is, according to him, incontestably the nerve 

 of taste; and, as this nerve is distributed to the mouth, we can under- 

 stand, why gustation should be effected there; but not how it can be 

 accomplished in the oesophagus and stomach. The tongue consists 

 almost entirely of muscles, which give it great mobility, and enable it 

 to fulfil the various functions assigned to it; for it is not only an organ 

 of taste, but of mastication, deglutition, and articulation. The muscles 

 being under the influence of volition, enable the sense to be executed 

 passively or actively. 



As regards gustation, the mucous membrane is the portion immedi- 

 ately concerned. This is formed, like the mucous membranes in gene- 

 ral, of the different layers already described. The corpus papillare 

 requires farther notice. If the surface of the tongue be examined, it 

 will be found to consist of myriads of fine papillae or villi, that give the 

 organ a velvety appearance. These papillae are, doubtless, like those 

 of the skin, formed of the final ramifications of nerves, and of the ra- 

 dicles of exhalant and absorbent vessels, united by means of a spongy 

 erectile tissue. Great confusion exists among anatomists in their de- 

 scriptions of the papillae of the tongue. Those certainly concerned in 

 the sense of taste may, however, be included in two divisions: 1st, the 

 conical or pyramidal, the finest sort by some called filiform; and 2dly, 



1 Precis de Physiol., i. 139. 



